The present invention relates to power semiconductor packages and methods of manufacturing power semiconductor packages.
Referring to FIGS. 1-4, a package 10 according to the prior art includes a conductive can 12, and a power semiconductor die 14. Can 12 is typically formed with an electrically conductive material such as copper or a copper-based alloy, and may be coated with silver, gold or the like. Die 14 may be a vertical conduction type power semiconductor MOSFET having its drain electrode 16 electrically and mechanically attached to an interior surface of can 12 by a conductive adhesive 18 such as solder or a conductive epoxy (e.g. silver epoxy). Source electrode 20, and gate electrode 22 of die 14 (which are disposed on a surface opposite to the drain electrode) each includes a solderable body which facilitates its direct connection to a respective conductive pad 24, 26 of a circuit board 28 by a conductive adhesive (e.g. solder or conductive epoxy) as illustrated by FIG. 4. Note that die 14 further includes passivation body 30 which partially covers source electrode 20 and gate electrode 22, but includes openings to allow access at least to the solderable portions thereof for electrical connection. Further note that in package 10 conductive can 12 includes web portion 13 (to which die 14 is electrically and mechanically connected), wall 15 surrounding web portion 13, and two oppositely disposed rails 32 extending from wall 15 each configured for connection to a respective conductive pad 34 on circuit board 28. Also, note that die 14 is spaced from wall 15 of can 12; i.e. wall 15 surrounds die 14. Thus, a moat 36 is present between die 14 and wall 15.
In a package according to the prior art, source electrode 20, and gate electrode 22 are soldered down by the user. Specifically, the user applies solder to, for example, the pads of a circuit board, and the electrodes of the die are attached to the pads by the solder so placed.
A package as described above is disclosed in U.S. Pat. No. 6,624,522.
To fabricate a package as described above, a solder is applied to drain electrode 16 of die 14, die is placed inside can 12, and the solder is reflown. Alternatively, solder is applied to the interior surface of web portion 13 of can 12, drain electrode 16 of die 14 is placed on the solder, and the solder is reflown. In each case, once the solder is reflown, there is a possibility that die 14 may move from its position as placed or become misaligned relative to its orientation as placed. As a result, the quality of the final product may be adversely affected.